The present invention relates to machines for comminuting tobacco, and more particularly to improvements in devices which are used to compress or compact tobacco in tobacco shredding machines. Still more particularly, the invention relates to improvements in chain conveyors which are used in tobacco compacting devices to convert tobacco leaves and/or fragments of tobacco leaves into a cake which is thereupon severed to yield tobacco shreds.
It is well known to equip a tobacco shredding machine with a compacting device wherein two endless chain conveyors converge to define a progressively narrowing channel for advancement of tobacco leaves toward the cutting station where the leader of the thus obtained tobacco cake is severed by one or more orbiting knives. The upper reach of the lower chain and the lower reach of the upper chain flank the channel and serve to entrain the tobacco leaves toward the severing station with simultaneous compacting of leaves to form the aforementioned cake. One of the chains can also serve as a counterknife in that it cooperates with the orbiting knife or knives in conversion of the leader of the cake into shreds.
The chains of tobacco compacting devices in tobacco shredding machines are subjected to highly pronounced stresses including bending and tensional stresses, to pronounced wear, as well as to contamination by certain constituents (especially the liquid constituents) of tobacco leaves. The liquid constituents penetrate into the spaces between the relatively movable parts of the chains. Attempts to avoid such undesirable influences and/or to avoid or eliminate the adverse effects of such influences include the making of extremely heavy, bulky and complex chains which should stand long periods of wear by being supposed to withstand the developing bending, tensional and/or other stresses.
As a rule, the front ends of the two endless chains which constitute component parts of the tobacco compacting or condensing device are adjacent to the respective portions of a mouthpiece through which successive increments of the cake advance into the range of the orbiting knife or knives of the shredding machine. The chains and the respective portions of the mouthpiece define narrow gaps which are barely sufficient to prevent frictional engagement between the chains and the mouthpiece but should not be wide enough to allow for penetration of larger particles of tobacco which could result in jamming of the conveyors and in mechanical damage to the parts of the compacting device. The gaps between the chains and the respective portions of the mouthpiece should be extremely narrow, normally in the range of a few tenths of one millimeter. In heretofore known tobacco shredding machines, the width of the just discussed gaps must be adjusted at rather frequent intervals due to pronounced wear upon the chains, especially in the regions where the chains are engaged by and receive motion from sprocket wheels. Thus, as the wear upon the chain parts which are driven by the sprocket wheels increases, the radii of curvature of the outer sides of the chain portions which are trained over the sprocket wheels and are adjacent to the respective portions of the mouthpiece also increase with the result that the gaps become wider and allow large particles of tobacco particles to penetrate thereinto.